Dr. Coico's studies continue to focus on the isolation and characterization of IgD receptors on T lymphocytes. Recent studies using the CD4+ human T cell line, MOLT 4, have shown that these cells expressed high levels of IgD-R. This was confirmed by immunofluorescent staining with a monoclonal antibody, LTB9. LTB9 is specific for a soluble form of IgD-R (i.e. IgD binding factor) and also reacts with membrane form. Biotinylated MOLT-4 cell membranes are being used as a source of IgD-R. Immunoprecipitation is performed after extensive preabsorption of solubilized membranes either with LTh9-Sepharose, or IgD- Sepharose. Electrophoretic profiles of such inmunoprecipitated proteins are identical and reveal two protein forms with MW's of approximately 90 and 70 Kda. (under reduced conditions). Large-scale immunoprecipitation experiments are underway to generate sufficient amounts of isolated IgD-R to allow us to perform peptide micro sequencing. Information derived from these experiments will ultimately facilitate our goal of cloning the IgD-R gene. Parallel studies, currently in progress, are aimed at identifying other membranes proteins associated with IgD-R as well as examining the possible roll of IgD-R in signal transduction.